The invention relates to operators for fluid flow control devices, such as valves, for example. In particular, this invention relates to operators for air valves, for example of the type including a manually engageable button mounted on a plunger for controlling the position of the plunger and thus the operation of the valve.
U.S. Pat. No. 4,790,208 shows a knob and shaft assembly for operating, for example, a vehicle air brake control valve. The assembly includes a knob having a front face and a barrel projecting from the face, and a shaft which is threadedly engaged with threads on the barrel. The assembly is provided with locking detents comprising protrusions on the shaft which are received within apertures on the barrel to releasably lock the knob to the shaft, thereby preventing the parts from being accidentally becoming disengaged. This also helps to assure the proper orientation of the knob with respect to the shaft to permit indicia embossed on the knob to be easily read by the operator.
In some vehicles, for example tractor-trailers with air brake systems, there is a module or assembly in which there are two vehicle air flow control devices (referred to herein as “switches”) next to each other, forming the assembly. The switches have plungers on which the switch buttons are mounted, with labels on the buttons.
In one such switch assembly, one device is labeled as a “red” switch, that is to be installed in a vehicle dashboard for controlling trailer air supply. The other device is labeled as a “yellow” switch, that is to be installed in a vehicle dashboard for controlling a different function, for example, parking brake. The switches are different colors to distinguish them.
Depending on the vehicle, the switch assembly can be mounted in the vehicle cab in either a horizontal (two switches left and right) orientation, or in a vertical orientation. In either case, when the switch assembly is in the installed position, the labels on the two buttons must be upright—that is, the text on the labels must be oriented upright for reading by the driver.
The buttons and switches may be manufactured so that either button can physically fit onto either switch, to minimize the number of unique parts, for cost purposes. In such a case, it is important that the buttons for the red and yellow switches not be swapped on their switches, to prevent having the incorrect switch be activated when the supposedly correct button is engaged.